The Clinical Translational (CT) Core addresses the challenges facing investigators who conduct human behavioral and biobehavioral research on IDD conditions, such as autism, fragile X syndrome, and Down syndrome. Participants can be difficult to recruit because of their relatively low prevalence in the general population. Moreover, once recruited, these participants require evaluations by professionals with specialized training to confirm diagnoses and determine whether inclusion/exclusion criteria are met. Recruitment of typically developing control participants can also be challenging, particularly for studies of young children that require biologic sampling or neuroimaging because parents are often reluctant to enroll. The CT Core is designed to help IDDRC investigators overcome these challenges by providing services that include participant recruitment, community outreach, initial diagnostic qualification, assessment of inclusion and exclusion criteria, and allocation of personnel and resources for these activities. The CT Core staff and resources dedicated to these activities will significantly diversify the available pool of participants; improve cost effectiveness efficiency, and productivity by sharing participant qualification characteristics across projects; and provide resources that are beyond the expertise or budget of specific investigators but are essential to the highest quality behavioral and biobehavioral science. The individuals and infrastructure associated with the proposed CT Core have provided similar services to many funded studies at the MIND Institute over the last dozen years, although these services were more limited in scope and were not previously integrated into a single organizational structure. The integration proposed and the expansion afforded by the support of the IDDRC U54 grant (and the additional institutional support of the MIND Institute and UC Davis) will increase efficiency, lower costs of services thereby encouraging greater use by IDDRC investigators, expand diagnostic evaluation services, and increase recruitment efforts, especially as regards the recruitment of ethnically, racially, and economically diverse participants. The primary objective of the CT Core is to establish and maintain an operational framework that is optimal for recruitment and diagnostic assessment and characterization of a diverse range of special and typical populations. We will achieve this objective by addressing the following Specific Aims: 1. Enhance recruitment of a diverse range of participants through a systematic process of community engagement, including multiple ethnicities, races, and economic backgrounds with both atypical and typical development across a wide age span. 2. Maintain a participant registry and tracking system that includes critical descriptive information, permitting investigators to select participants for recruitment who are most likely to meet specific eligibility criteria. 3. Provide experienced evaluators who can advise studies in best practices for diagnostic assessment and standardized measure selection, provide training in administration of standardized measures, establish initial reliability and ongoing monitoring of administration fidelity, and conduct specialized diagnostic assessments as needed.